Nasal cavity

Nose

The external nasal anatomy is quite simple. It is a pyramidal structure, with its root located superiorly and apex sitting inferiorly. The root is continuous with the anterior surface of the head and the part between the root and the apex is called the dorsum of the nose. Inferior to the apex are the two nares (nostrils), which are the openings to the nasal cavity. The nares are separated by the nasal septum and are laterally bounded by the ala nasi (wings of the nostrils).

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The external nose is comprised of both bony and cartilaginous components. The bony part shapes the nose root, formed by the nasal, maxillae and frontal bones. The cartilaginous part is located inferiorly and is comprised of several alar, two lateral, and one septal cartilage:

• Alar cartilages; major alar cartilage forms the apex of the nose, minor alar cartilages support the ala nasi
• Lateral processes of the septal cartilage; form the dorsum of the nose
• Septal cartilage; bounds the nares medially

Note that the septal cartilage is attached to both the bony nasal septum (which is actually the perpendicular plate of the ethmoid bone) and the vomer bone. Both nasal septum and vomer are bony parts of the internal nose.

Nasal cavity

The internal part of the nose is the nasal cavity. The two nasal cavities sit within the external nose and the adjacent skull. The cavities open anteriorly to the face through the two nares. Posteriorly the cavities communicate with the nasopharynx by two apertures called choanae. 

Besides the anterior and posterior apertures, each nasal cavity has a roof, floor, and lateral and medial walls. There are 12 cranial bones in total that contribute to the nasal cavity structure, which include the paired nasal, maxilla, palatine and lacrimal bones, as well as the unpaired ethmoid, sphenoid, frontal and vomer bones.

Among all of them, the ethmoid bone is the most important element, for two reasons: first, it makes the greatest portion of the nasal skeletal framework by forming the roof and walls of the nasal cavities; and second, it contains ethmoidal cells which, as a group, are one of the four paranasal sinuses. 

The nasal bones can easily be remembered by using this mnemonic: Nerdy Medical Students are often Very PaLE (Nasal, Maxilla, Sphenod, Vomer, Palatine, Lacrimal, Ethmoid)

Want to know everything about the ethmoid bone? We got you covered with these study units:

Three bony shelves called the inferior, middle and superior nasal conchae are attached to the lateral walls and by projecting into the cavities, they divide both nasal cavities into four air channels:

• Inferior nasal meatus; between the floor and inferior concha
• Middle nasal meatus; between the inferior and middle concha
• Superior nasal meatus; between the middle and superior concha
• Sphenoethmoidal recess; between the superior concha and the nasal cavity roof
• Common nasal meatus: between the conchae and nasal septum

The nasal cavity is divided into three regions, aligned as if a three floor building. The vestibule is located just inside the anterior external opening of the nose (1st floor) and it contains hair follicles. The largest region is the respiratory region, which is lined with respiratory epithelium (2nd floor). Finally, there is the olfactory region, a small area located inside the skull at the superior apex of the cavity, which is lined with olfactory cells and receptors (3rd floor).

The two nasal cavities communicate with four bony recesses called the paranasal sinuses. They are named according to the bones they are placed within, as the: sphenoidal, maxillary, and frontal sinuses, and the ethmoidal cells. All of the sinuses are covered by respiratory mucosa and innervated by the trigeminal nerve (CN V). 

To learn everything about the nasal cavity in a fun and engaging way, check out the custom quiz and clinical case. 

Blood supply

The nose is supplied by branches of both the external and internal carotid arteries. The external carotid artery sends the sphenopalatine, greater palatine, superior labial and lateral nasal arteries which mostly supply the vestibule and respiratory portions of the nasal cavity, as well as the surrounding parts of the external nose (apex and dorsum).The internal carotid artery gives off the anterior and posterior ethmoidal arteries which mostly supply the apex of the nasal cavity and the surrounding part of the external nose. Many of the external and internal carotid arterial branches anastomose at the anterior part of the medial wall. This particular spot is the place from where the most nosebleeds occur.

Learn more about the blood supply of the nose, and which part of the nose each branch supplies, from this resource:

Nerve supply

The nose is innervated by three cranial nerves:

• Olfaction is provided by the olfactory nerve (CN I)
• General sensation is carried by the trigeminal nerve (CN V)
• Serous glands in the nasal mucosa which produce fluid that constantly lubricates the nose walls are innervated by the parasympathetic fibers of the facial nerve (CN VII). Sympathetic innervation comes from T1 level of spinal cord and is intended for regulation of blood flow through mucosa

To solidify your knowledge about the nerves that supply the nose, try out our quiz:

Related articles

Articles within this topic:

• Choana
• Kiesselbach’s plexus
• Lateral wall of the nasal cavity
• Medial wall of the nasal cavity
• Nasal conchae
• Nasal septum
• Nasal vestibule
• Nostrils
• Olfactory epithelium
• Ostiomeatal complex
• Paranasal sinuses
• Waldeyer’s ring